Grossherr M, Hengstenberg A, Meier T, Dibbelt L, Igl B W, Ziegler A, Schmucker P, Gehring H
Department of Anaesthesiology, University of Luebeck, Ratzeburger Allee 160, D-23538 Luebeck, Germany.
Br J Anaesth. 2009 May;102(5):608-13. doi: 10.1093/bja/aep053. Epub 2009 Mar 31.
Measuring propofol concentration in plasma (c(P)PL) and in exhaled alveolar gas (c(P)G) during constant infusion provides information about their respective time courses. In the present study, we compared these time courses in patients undergoing cardiac surgery from the beginning of propofol anaesthesia until eye opening upon awakening.
The c(P)G was measured before, during, and after continuous infusion of propofol for general anaesthesia in 12 patients at two randomly allocated doses (3 or 6 mg kg(-1) h(-1)). Gas samples were collected on Tenax tubes. After thermodesorption, c(P)G was measured by gas chromatography mass spectrometry. Simultaneously with exhaled gas, arterial blood was sampled for measuring c(P)PL by reversed-phase high-performance liquid chromatography with fluorescence detection. In order to compare the time courses of c(P)PL and c(P)G as dimensionless values directly, each gas and plasma value was normalized by relating it to the corresponding value at the end of the initial infusion after 40 min.
The c(P)G ranged between 2.8 and 22.5 ppb, whereas the corresponding c(P)PL varied between 0.3 and 3.3 microg ml(-1). Normalized concentration values showed a delayed increase in c(P)G compared with c(P)PL under constant propofol infusion before the onset of cardiopulmonary bypass, and a delayed decrease after stopping the propofol at the end of anaesthesia.
Propofol can be measured in exhaled gas from the beginning until the end of propofol anaesthesia. The different time courses of c(P)PL and c(P)G have to be considered when interpreting c(P)G.
在持续输注异丙酚过程中，测量血浆中异丙酚浓度（c(P)PL）和呼出肺泡气中异丙酚浓度（c(P)G）可提供有关它们各自时间进程的信息。在本研究中，我们比较了心脏手术患者从异丙酚麻醉开始至苏醒睁眼期间这些时间进程。
在12例患者中，以两种随机分配的剂量（3或6 mg·kg⁻¹·h⁻¹）持续输注异丙酚进行全身麻醉，在输注前、期间和之后测量c(P)G。气体样本收集在Tenax管上。热解吸后，通过气相色谱 - 质谱法测量c(P)G。与呼出气体同时，采集动脉血，通过反相高效液相色谱荧光检测法测量c(P)PL。为了直接比较c(P)PL和c(P)G作为无量纲值的时间进程，将每个气体和血浆值通过将其与初始输注40分钟后结束时的相应值相关联进行归一化。
c(P)G范围在2.8至22.5 ppb之间，而相应的c(P)PL在0.3至3.3 μg·ml⁻¹之间变化。在体外循环开始前持续输注异丙酚时，归一化浓度值显示c(P)G相对于c(P)PL延迟升高，在麻醉结束时停止输注异丙酚后c(P)G延迟降低。
在异丙酚麻醉从开始到结束的整个过程中，均可在呼出气体中测量异丙酚。在解释c(P)G时，必须考虑c(P)PL和c(P)G不同的时间进程。
